Field of the Invention
Rotary dampers of various types and configurations are conventionally used on rotating machinery to inhibit the occurence of unwanted oscillations. These oscillations adversely affect machine performance and can result in permanent damage to the machine itself if left unchecked. Rotary dampers commonly embody a viscous fluid which impedes the undesired motion and absorbs the energy associated therewith. A primary problem associated with existing viscous dampers has been the mechanical seals which retain the viscous fluid in the damping chamber. These seals are subject to wear and eventually leak resulting in a loss of the damping fluid. Loss of the fluid degenerates the damping effectiveness of the device and the continued operation of the machine may cause serious damage as a result of the undamped oscillations.
A viscous magnetic fluid damper is disclosed herein which substantially reduces the leaky seal problem. The magnetic fluid is retained in the damper by magnetic forces and the requirement for mechanical fluid seals and their attendant problems are substantially eliminated.
Magnetic or ferromagnetic fluids are well known in the art and are commercially available. Briefly, magnetic fluids are a mixture of a high permeability material, such as iron or iron oxide in a fluid medium such as oil, grease, or other fluids. Since their conception, magnetic fluids have been used in a wide variety of energy absorbing devices, such as shock absorbers, fluid dampers, magnetic clutches and even for the recoil mechanism of large artillery pieces and guns. Typical uses of magnetic fluids may be found in U.S. Pat. No. 2,667,237 "Magnetic Fluid Shock Absorber" by R. E. Gunther (August, 1958), U.S. Pat. No. 2,669,325 "Energy Absorber" by A. Raines (February, 1954), U.S. Pat. No. 2,973,969 "Electrical Shock Absorbing System" by E. S. Thall (March, 1961), and U.S. Pat. No. 3,006,656 "Automatic Accessory Control for Magnetic Particle Shock Absorber" by B. H. Schaub (October, 1961). These patents ostensibly teach devices which utilize the variation in viscosity of the magnetic fluid with the intensity of the applied magnetic field, and embody electromagnets to control the intensity of the magnetic field. Raines, in U.S. Pat. No. 2,669,325, discloses a linear viscous damper for a gun recoil mechanism which uses permanent magnets and a magnetic fluid. Mechanical means are provided for varying the intensity of the magnetic field generated by the permanent magnets to adjust for change and climatic conditions.